1. Field of the Invention
The present invention relates generally to network systems and methods which provide voice communications through a packet network, and more specifically, to network systems and methods for providing efficient voice communication through a packet network such as the Internet.
2. Description of the Related Art
A conventional telephone network 100 is illustrated in FIG. 1 and comprises, inter alia, a plurality of toll offices, such as toll offices (TS) 105 and 110, that may be interconnected to one another to provide long distance voice and data communications for subscribers, such as the telephone users, associated with station sets S1 and S2. The manner in which a telephone user, for example, the user associated with the station S1, establishes via network 100 a telephone connection to another such user, for example, the user associated with the station S2, is well known and will not be described in detail herein. However, it suffices to say that a telephone user, hereinafter also a subscriber, may establish such a connection by causing the station S1 to go off hook and then dialing the telephone number associated with the station to which he wishes to connect, such as the station S2. Local central office 50 associated with station S1 collects the telephone digits as they are dialed and establishes a connection 101 to a network toll office, for example, toll office 105 which may also be referred to hereinafter as a toll switch. Toll office, or switch 105, in turn, and based on the dialed telephone number that it receives from the local central office 50, establishes a connection 102 to a so-called destination toll switch, such as toll switch 110. Destination toll switch 110, in turn, extends the connection to central office 75 associated with the station S2 and passes to that office the dialed telephone number. The latter central office responsive to receipt of the dialled digits then extends the connection 103 to station S2. The subscribers positioned respectively at stations S1 and S2 may then begin to speak to one another via the established connection.
Since the charges for long distance services, that is, for connections such as the link between toll switches 105 and 110, typically amount to several dollars for every hour of connection time, lower-cost alternatives would be highly desirable. With the growth of the Internet and the increasing sophistication of Internet subscribers, the Internet could be employed to provide the long distance portion of such a telephone call. Since Internet access is often provided for a few tens of dollars per month, employing the Internet in this manner could save a frequent user hundreds of dollars per month. Even though the Internet is a relatively lossy medium due to the system overheads from uncontrolled access, telephone connections of acceptable quality are possible. Current Internet-based long distance services permit a user to dial a local access number which connects the user to an Internet Telephone Gateway (ITG). The ITG prompts the user for a destination telephone number, then routes the call over the Internet to a similar device at the local exchange of the destination and the destination ITG dials the end user, thereby completing the link. Although such services permit an Internet user to establish a telephone call, using the Internet for the long distance portion of the call, current approaches tend to employ protocols to establish and tear down a new Internet connection with each individual call and the conventional Internet protocols used to establish telephone calls are relatively inefficient, requiring excessive overhead, because the protocols were established to provide extensive feature sets for digital communications links, not for voice communications which, with analog telephones operating at either endpoint, do not require and cannot use the feature sets. Additionally, voice communications at relatively low data-rates are supported by emerging system components. That is, new coder/decoders (codecs) are emerging which can support near toll-quality voice communications at only 8 kilobits per second (kbps) and acceptable quality at 4 kbps. These low data rate codecs can significantly reduce the cost of providing ITG services.
Consequently, it would be highly desirable to provide long distance telephone services over a packet network, such as the Internet, and to increase the efficiency of the connections thereby established while supporting low data rate voice communications. Additionally, voice applications are important for other packet networks, such as the connection of private branch exchanges or the connection of voice access switches by a packet network. Improvements in efficiency are highly desirable for these applications as well.